Polarized magnet arrangement



March 8, 1960 P. o. R. PERsoN POLARIZED MAGNET ARRANGEMENT Filed March 20, 1957 Lvmswrok PM? 01.0; PAM/4x Paine/v firronuzys Ua fid SW Pa POLARIZED MAGNET ARRANGEMENT Per Olof Ragnar Persson, Sundbyberg, Sweden, assignor to Telefonaktiebolaget L M Ericsson, Stockholm, Sweden, a corporation of Sweden Application March 20, 1957, Serial No. 647,303

4 Claims. (Cl. 317-172) The present invention refers to a polarized magnet arrangement of the kind that includes a closed magnetic circuit path, a winding adapted to be connected to a source of alternating current for generating a magnet flux through said path, and a permanent magnet, one pole of which faces the magnetically closed circuit path the other pole of which faces the centre of a movably arranged armature, the magnetically closed circuit and the movably arranged armature being so constructed and placed relatively each other that at the ends of the armature there are defined two for magnetic fluxes suitable air gaps, the size of which at a given moment of time is dependent on the relative position of the armature at the time mentioned.

Hitherto known similar arrangements have been made so that either the magnetic circuit has not been entirely closed, whereby the existing polarized flux from the magnet and the alternating flux from the coil do not coincide satisfactorily in the air gaps, or with the magnetic circuit entirely closed they have been constructed so that the joining of the existing fluxes has occurred already at a substantial distance from the air gaps, whereby certain parts of the magnetic circuit have had to be dimensioned relatively large.

The mentioned disadvantages are avoided and a great simplicity in construction and production is attained with a polarized magnet arrangement according to the present invention, which arrangement is characterized by the magnetic closed circuit having mainly the form of a M, the free ends of the outer legs being connected to each other and the remaining ends of the outer legs forming a limiting surfacefor each one of the mentioned air gaps, one pole of the mentioned permanent magnet facing the bottom of the concave part connecting the mentioned remaining ends,

The invention will be described more in detail in connection with the drawing, where Fig. 1 shows schematically a polarized magnet arrangement according to the invention, Fig. 2 shows a part of a polarized alternating current hell with a magnet arrangement according to Fig. l, and Figs. 3 and 4 show more in detail certain features of the arrangement according to Fig. 2.

The arrangement according to Fig. 1 comprises a mag netically closed circuit path in the form of a M frame 1, the free ends of the outer legs 13 and 14 being connected to each other by a core 12 supporting a coil 21. The remaining ends 15 and 16 of the outer legs 13 and 14 each form a limiting surface for an air gap 2 respectively 3, the other limiting surface of which is defined by an armature 4 movably arranged about a pivot 41. The size of the air gaps 2 and 3 is also dependent on the position of the armature 4 relatively the magnetically closed frame 1. A permanent magnet is with oneof its poles (the north-pole) turned towards the bottom 18 of the concave part 17-18-19 connecting the other ends and 16. The remaining pole of the permanent magnet 5 (the south-pole) faces the centre of the armature 4, that is the axis of rotation of the armature; between the permanent magnet 5 and the armature 4 there is a small air gap 6. The ends of the armature 4 are suitably provided in a well-known way with pole studs 42 to prevent sticking. The slanted connection links 17 and 19, which connect the bottom 18 with the remaining ends 15 and 16, are dimensioned so that they are saturated by the magnet flux coming from the permanent magnet 5. For instance they can be given smaller section area than the remaining parts of the circuit path by means of suitably placed notches. This aifords the advantage that the bottom 18 under the magnet 5 does not need to be saturated, whereby unnecessary leakage fluxes are avoided. When coil 21 connected to a source of alternating voltage, an alternatingfiux is generated, which in Fig. 1 is indicated by a line of short dashes for a certain moment. The permanent flux from the magnet 5 is indicated by two continuous lines. With the flux directions, as indicated in Fig. 1, the fluxes will cooperate in the air gap 2 but counteract each other in the air gap 3, whereby the armature 4 will pivot to the left. During the next half period of the alternating voltage the direction of the flux from the coil will be reversed, that is the armature will pivot to the right.

As can be seen from Fig. l the two magnet fluxes do not join until the area is reached, where they are needed, namely the surfaces defining the air gaps 2 and 3. By this any overdimensioning of the parts included in the magnetically closed circuit path is not necessary. From the point of production, this renders the structure very simple, for the principal part of the circuit path, the M-formed pole-forming 'part, can easily be shaped from a band of suitable material.

'In the arrangement according to Fig. 2 the magnetically closed circuit 12131718-19-14 is formed. The core 12 is here provided with threaded ends, which project through the outer legs 13 and 14, and are secured by nuts 20, one on each side of the winding 21. An U- formed clamp 7 held by means of screws 71 straddles the magnet circuit path. Clamp 7 also serves to secure the magnet 5 by pressing a spring 72 against the magnet, see especially Fig. 3, and to hold pivot pin 41 for the armature 4. The pin 41 is squeezed between the armature 4 and a clapper bar 42 tightened to the armature by screws 44. The pin 41 projects with its two ends into shanks of the clamp 7. Fig. 4 shows the armature 4 with its pin 41 and two threaded holes in the armature for the screws 44.

Of course, a polarized magnet arrangement according to the invention is not limited to the fields of use mentioned before; it can also be used in many other technical fields, as for instance for telephone receiver a.s.o. where great demands are made upon simple construction, security of function and low prices.

I claim:

1. A polarized electro-magnetic structure comprising a substantially M-shaped magnetic frame having two substantially parallel outer legs and two middle legs slanted toward each other, a core member joining the free ends of the two outer legs of said frame, an exciting coil seated upon said core member and adapted to be connected to a source of alternating current, a permanent magnet facing with one pole the valley between the two apices of the M-shaped frame defined by the two slanted middle legs of the frame, and an armature bar supported pivotal about a pivot point situated in alignment with the other pole of the magnet spaced apart therefrom, each end of said armature bar and the adjacent apex of the M-shaped frame defining an air gap therebetween, said coil when excited generating an alternating magnetic flux closing through the core member, the outer legs, the air gaps and the armature, and the permanent magnet generating rltenied Mar. 8, 1960 magnetic fluxes closing through the magnet, the middle legs, the air gaps and the armature, whereby the angular position of the armature bar relative to the frame is controlled by the direction of. the. current flow through the coil.

, 2 A polarized structure according to claim 1' wherein the frame portions joining the apex portions and the valley portion of the frame are dimensioned to be substantially saturated by the magnetic field of the permanent magnet. 3. A polarized structure according to claim 1 wherein the ends of the middle legs opposite to the apices defining ends thereof are joined by a leg portion disposed transversely of said outer legs, and wherein said permanent magnet is in the form of a bar magnet rising from said leg portion toward the armature.

, 4. A. polarized electro-magnetic structure for an electric bell, comprising a substantially M-shaped magnetic frame having two substantially parallel. outer legs and two middle. legs slanted toward each other, a. core member joining the free ends of the two outer legs of said frame, an exciting coil seated upon said core member and adapted to be connected to a source of alternating current, a permanent magnet facing with one pole the valley between. the two apices of the M-shaped frame defined by the two middle legs of the frame, an armature bar supported pivotally about a pivot point situated in alignment with the other pole of the magnet spaced apart therefrom, each end of said armature bar and the adjacent apex of said M-shaped frame defining an airgap therebetween, said coil when excited generating an alternating magnetic flux closing through the core member, the outer legs, the air gaps and the armature, and the permanent magnet generating magnetic fluxes closing through the magnet, the middle legs, the air gaps and the armature, whereby the angular position of the armature bar relative. to the frame is controlled by the direction of the current flow through the coil, and a bell clapper secured to said armature bar for reciprocatory pivotal movement in unison therewith.

References Cited in the file of this patent UNITED STATES PATENTS 1,901,443 Garvin Mar. 14, 1933. 2,499,200 Somerville Feb. 28, 1950 2,740,057 Blumenstock et a1. Mar. 27, 1956 2,759,114 Rolli et al Aug. 14, 1956 FOREIGN PATENTS 209,749 Switzerland July 16, 1940 

